Disclosed herein is an apparatus and method that cleans a photoreceptor in a printing apparatus.
Presently, printing devices, such as printers, multifunction media devices, xerographic machines, and other devices produce images on media sheets, such as paper, substrates, transparencies, plastic, cardboard, or other media sheets. To produce an image, marking material, such as toner or other marking material, is applied to a photoreceptor. The marking material is then transferred from the photoreceptor to the media sheet to create an image on the media sheet.
Electrostatic cleaning brushes are designed to remove small amounts of toner remaining on the photoreceptor after incomplete transfer to the media sheet and much larger amounts of toner on the photoreceptor when transfer has been disabled. Typical normal operation transfers 90% or more of the image toner on the photoreceptor to the media sheet. The residual 10% or less of the developed image toner can be cleaned by the electrostatic brush at a relatively low voltage bias. When transfer has been disabled, 100% of the developed image toner must be cleaned. Cleaning this much larger amount of toner requires a higher voltage bias and sometimes more than one cleaning pass through the cleaner. Transfer is typically disabled in normal operation for process control patches developed in the inter-document zones on the photoreceptor, in performance of a process control adjustment or diagnostic routine, or in recovery from a paper jam where the print media has failed to arrive at transfer.
Unfortunately, excessive filming of the photoreceptor surface occurs under certain operating conditions. Electrostatic cleaning brushes can be used to reduce photoreceptor filming by wearing the photoreceptor surface. To prevent unwanted film generation, and the associated image quality defects, the wear rate of the photoreceptor from the cleaning brushes must be maintained sufficiently high at design time to prevent excessive film buildup. However, a variety of noise factors affect the rate of film generation, so it is somewhat difficult to predict the required film removal rate across all potential conditions. As a result, a tradeoff must currently be made that results in excessive photoreceptor wear across many situations. In fact, there has been concern about having too low of a photoreceptor wear rate in some printing devices. Design time optimization across the entire gamut of potential operating conditions leads to higher photoreceptor wear rates than required for many printing devices, resulting in higher run costs.
For example, an electrostatic brush cleaner system can use a combination of mechanical disturbance and applied bias, such as an electric field, to effect toner removal from a photoreceptor surface. In most print engines, the bias applied to the brushes is determined at design time. The bias chosen is typically the value required to clean the largest stress input of toner in one or two passes through the cleaner. Unfortunately, the use of a fixed bias results in unnecessary wear on the photoreceptor in all but the highest stress conditions.
Thus, there is a need for an apparatus and method that cleans a photoreceptor in a printing apparatus by adjusting a cleaning brush bias.